The SR-556 is a semi-automatic AR-15 style rifle manufactured by Sturm, Ruger & Co. The rifle was introduced in 2009 in .223 Remington/5.56×45mm NATO and as a .308 Winchester AR-10 variant in 2013, the SR-762. It is one of several AR-15 rifles to use a gas piston operation.
Ruger SR-556 - Standard Configuration (discontinued)
Firing the Ruger SR-556
Adjustable gas key on Ruger SR-556 piston rifle
Elements of Ruger SR-556 gas system
An AR-15–style rifle is a lightweight semi-automatic rifle based on or similar to the Colt AR-15 design. The Colt model removed the selective fire feature of its predecessor, the original ArmaLite AR-15, itself a scaled-down derivative of the AR-10 design by Eugene Stoner. It is closely related to the military M16 rifle.
Rifles styled like the AR-15 come in many sizes and have many options, depending on the manufacturer. The lower receiver, without the receiver extension, rear takedown pin, and buttstock, is shown at bottom.
A stripped lower receiver, one that is lacking the additional parts included in a completed lower receiver, is the only part of an AR-15–style rifle that needs to be transferred through a federally licensed firearms dealer under United States federal law.
American Tactical OMNI AR-15–style rifle (lower in polymer), 5.56×45mm NATO caliber, with Millett DMS-1 scope and FAB Defense stock and grips
